Transferring snapshot copy to object store with deduplication preservation and additional compression

ABSTRACT

Techniques are provided for incremental snapshot copy to an object store. A list of deallocated block numbers of primary storage of a computing device are identified. Entries for the list of deallocated block numbers are removed from a mapping metafile. A list of changed block numbers corresponding to changes between a current snapshot of the primary storage and a prior copied snapshot copied from the primary storage to the object store is determined. The mapping metafile is evaluated using the list of changed block numbers to identify a deduplicated set of changed block numbers without entries within the mapping metafile. An object, comprising data of the deduplicated set of changed block numbers, is transmitted to the object store for storage as a new copied snapshot.

RELATED APPLICATION

This application claims priority to and is a continuation of U.S.application Ser. No. 16/296,424, filed on Mar. 8, 2019, now allowed,titled “TRANSFERRING SNAPSHOT COPY TO OBJECT STORE WITH DEDUPLICATIONPRESERVATION AND ADDITIONAL COMPRESSION,” which is incorporated hereinby reference.

BACKGROUND

Many users utilize cloud computing environments to store data, hostapplications, etc. A client device may connect to a cloud computingenvironment in order to transmit data from the client device to thecloud computing environment for storage. The client device may alsoretrieve data from the cloud computing environment. In this way, thecloud computing environment can provide scalable low cost storage.

Some users and businesses may use or deploy their own primary storagesystems such as clustered networks of nodes (storage controllers) forstoring data, hosting applications, etc. A primary storage system mayprovide robust data storage and management features, such as datareplication, data deduplication, encryption, backup and restorefunctionality, snapshot creation and management functionality,incremental snapshot creation, etc. However, storage provided by suchprimary storage systems can be relatively more costly and less scalablecompared to cloud computing storage. Thus, cost savings and scalabilitycan be achieved by using a hybrid of primary storage systems and remotecloud computing storage. Unfortunately, the robust functionalityprovided by primary storage systems is not compatible with cloudcomputing storage, and thus these features are lost such as compressionand deduplication otherwise provided by a primary storage system.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a component block diagram illustrating an example clusterednetwork in which an embodiment of the invention may be implemented.

FIG. 2 is a component block diagram illustrating an example data storagesystem in which an embodiment of the invention may be implemented.

FIG. 3 is a flow chart illustrating an example method for incrementalsnapshot copy to object store.

FIG. 4A is a component block diagram illustrating an example system forincremental snapshot copy to object store.

FIG. 4B is a component block diagram illustrating an example system forincremental snapshot copy to object store, where a list of deallocatedblock numbers is identified.

FIG. 4C is a component block diagram illustrating an example system forincremental snapshot copy to object store, where a list of changed blocknumbers are identified.

FIG. 4D is a component block diagram illustrating an example system forincremental snapshot copy to object store, where data of a deduplicatedset of changed block numbers is created and store into an object store.

FIG. 5 is an example of a computer readable medium in which anembodiment of the invention may be implemented.

FIG. 6 is a component block diagram illustrating an example computingenvironment in which an embodiment of the invention may be implemented.

DETAILED DESCRIPTION

Some examples of the claimed subject matter are now described withreference to the drawings, where like reference numerals are generallyused to refer to like elements throughout. In the following description,for purposes of explanation, numerous specific details are set forth inorder to provide an understanding of the claimed subject matter. It maybe evident, however, that the claimed subject matter may be practicedwithout these specific details. Nothing in this detailed description isadmitted as prior art.

Many users want primary storage system services, such as datareplication, data deduplication, compression preservation, encryption,backup and restore functionality, snapshot creation and managementfunctionality, etc. to be compatible with cloud storage provided by acloud storage environment. In an example, primary data accessed byclient devices may be stored within a primary storage system andsecondary data (e.g., replicated primary data and copied snapshot data)may be stored in the cloud storage environment in order to reduce anoverall total cost of ownership of the secondary data because cloudstorage is more cost effective than primary storage. However, manyprimary storage system services are incompatible with the cloud storageenvironment, and thus such features are unavailable.

Accordingly, methods and systems are provided herein for copyingsnapshots from a computing device (e.g., a node, an on-premise device, astorage controller, a computer, or any other hardware or software suchas software as a service capable of managing storage of a primarystorage system such as a cluster of computing devices) to an objectstore (e.g., a cloud computing environment) in a manner that preservesdeduplication and compression used by the computing device. The presentsystem provides for incrementally copying snapshots of a file system ofprimary storage of the computing device to the object store as copiedsnapshots comprised of data stored within objects of the object store.That is, when a current snapshot, maintained by the computing device, isto be copied to the object store, merely unique data blocks of thecurrent snapshot compared to data blocks of already copied snapshots(e.g., data blocks already stored in the object store) are copied whileother non-unique blocks are not copied. This incremental copyingpreserves deduplication and reduces network bandwidth utilization andstorage utilization of the object store in order to reduce overall costof ownership of storing copied snapshots in the object store. Thepresent system can represent each snapshot as a fully logical copy thatis fully independent, which enables a simplified representation ofsnapshot data, and simplifies access and version management of snapshotdata. A copied snapshot is fully independent because the copied snapshotcan be accessed, in some embodiments, without having to reference or useother copied snapshots (e.g., a single file or any other amount of datacan be restored using merely the copied snapshot without having toreference other copied snapshots).

The present system preserves deduplication and compression used by thecomputing device for snapshots when storing copied snapshots to theobject store notwithstanding copied snapshots representing fully logicalcopies of data in the primary storage of the computing device. Inparticular, deduplication is preserved because data that is shared in asnapshot (e.g., a local or primary snapshot created and maintain by thecomputing device) is also shared in a copied snapshot in the objectstore. Deduplication of compression groups is maintained while logicallyrepresenting the compression groups in a copied snapshot. Block sharingacross multiple snapshots is also preserved so that merely changedblocks are transferred/copied to the object store during incrementalsnapshot transfers.

The present system provides additional compression on a snapshot datacopy. In particular, larger compression groups provide more spaceefficiency but with less read efficiency compared to smaller compressiongroups. Relatively smaller compression groups may be used by thecomputing device of the storage system since access to the primarystorage of the computing device may be more read intensive, and thusread efficiency is prioritized over storage space efficiency. Becausecopied snapshots in the object store are infrequently accessed (e.g.,cold data that is infrequently read), relatively larger compressiongroups can be employed for improved storage space efficiency within theobject store, which also reduces network bandwidth for snapshot copyingto the object store.

In one embodiment, snapshots maintained by a computing device are copiedto an object store, such as a cloud computing environment, as copiedsnapshots representing logical data of the snapshots. Data of the copiedsnapshots is stored into slots of objects that are deduplicated withrespect to other objects stored within the object store and retaincompression used by the computing device for the snapshots.

In an example, the computing device stores data within primary storage.The computing device may create snapshots of the data stored by thecomputing device. For example, the computing device may create asnapshot of a file, a logical unit number, a directory, a volume, astorage virtual machine hosting a plurality of volumes, a file system, aconsistency group of any arbitrary grouping of files, directories, ordata, etc. The computing device may deduplicate data between thesnapshots so that instead of storing redundant data blocks multipletimes, merely references are stored in place of the redundant datablocks and point to original data blocks with the same data. Thecomputing device may compress data within the snapshots, such as bycreating compression groups of compressed data blocks.

As provided herein, in order to benefit from the storage cost savingsand scalability of the object store, the snapshots are copied to theobject store as copied snapshots. In an example, a snapshot of a filesystem of the computing device is to be copied to the object store. Amapping metafile and/or an overflow mapping metafile are used tofacilitate the copying of the snapshots to the object store in a mannerthat preserves deduplication and compression, logically represents thesnapshots as fully independent snapshots, and provides additionalcompression.

The mapping metafile is populated with entries for block numbers (e.g.,virtual volume block numbers, physical volume block numbers, etc. usedby the computing device to reference data such as snapshot data storedby the computing device) of snapshots maintained by the computing deviceand copied into objects of the object store as copied snapshots. Anentry within the mapping metafile is populated with a mapping between ablock number of data within a snapshot at the computing device (e.g., avirtual volume block number) and a cloud block number (e.g., a cloudphysical volume block number) of a slot within an object into which thedata was copied when the snapshot was copied to the object store as acopied snapshot. The entry is populated with a compression indicator toindicate whether data of the block number is compressed or not (e.g., abit set to a first value to indicate a compressed virtual volume blocknumber and set to a second value to indicate a non-compressed virtualvolume block number).

The entry is populated with a compression group start indicator toindicate whether the block number is a starting block number for acompression group of a plurality of block numbers of compressed datablocks. The entry is populated with an overflow indicator to indicatewhether the data block has an overflow entry within the overflow mappingmetafile. The overflow mapping metafile may comprise a V+ tree, such asa special B+ tree with support for variable length key and payload so akey can be sized according to a type of entry being stored foroptimization. The key uniquely represents all types of entriesassociated with a block number (a virtual volume block number). The keymay comprise a block number field (e.g., the virtual volume block numberof a data block represented by the block number or a starting virtualvolume block number of a first data block of a compression groupcomprising the data block), a physical length of an extent of the datablock, if the corresponding entry is a start of a compression group, andother block numbers of blocks within the compression group. The payloadis a cloud block number (a cloud physical volume block number). Theentry may be populated with a logical length of an extent associatedwith the block number. The entry may be populated with a physical lengthof the extent associated with the block number.

The mapping metafile and/or the overflow mapping metafile may be indexedby block numbers of the primary storage (e.g., virtual volume blocknumbers of snapshots stored by the computing device within the primarystorage, which are copied to the object store as copied snapshots). Inan example, the block numbers may correspond to virtual volume blocknumbers of data of the snapshots stored by the computing device withinthe primary storage. In an example, a block number corresponds to astarting virtual volume block number of an extent of a compressiongroup.

The mapping metafile and/or the overflow mapping metafile is maintainedaccording to a first rule specifying that the mapping metafile and/orthe overflow mapping metafile represent a comprehensive set of cloudblock numbers corresponding to a latest snapshot copied to the objectstore. The mapping metafile and/or the overflow mapping metafile ismaintained according to a second rule specifying that entries within themapping metafile and/or the overflow mapping metafile are invalidatedbased upon any block number in the entries being freed by the computingdevice.

The mapping metafile and/or the overflow mapping metafile is used todetermine what data of the current snapshot is to be copied to theobject store and what data already exists within the object store sothat only data not already within the object store is transmitted to theobject store for storage within an object. Upon determining that thecurrent snapshot is to be copied to the object store, an invalidationphase is performed. In particular, a list of deallocated block numbersof primary storage of the computing device (e.g., virtual volume blocknumbers, of the file system of which snapshots are created, that are nolonger being actively used to store in-use data by the computing device)are determined based upon a difference between a first snapshot and asecond snapshot of the primary storage (e.g., a difference between abase snapshot and an incremental snapshot of the file system). As partof the invalidation phase, entries for the list of deallocated blocknumbers are removed from the mapping metafile and/or the overflowmapping metafile.

After the invalidation phase, a list of changed block numberscorresponding to changes between the current snapshot of the primarystorage being copied to the object store and a prior copied snapshotalready copied from the primary storage to the object store isdetermined. The mapping metafile is evaluated using the list of changedblock numbers to identify a deduplicated set of changed block numberswithout entries within the mapping metafile. The deduplicated set ofchanged block numbers correspond to data, of the current snapshot, notyet stored within the object store.

An object is created to store data of the deduplicated set of changedblock numbers. The object comprises a plurality of slots, such as 1024or any other number of slots. The data of the deduplicated set ofchanged block numbers is stored into the slots of the object. An objectheader is updated with metadata describing the slots. In an example, theobject is created to comprise the data in a compressed statecorresponding to compression of the data in the primary storage. Theobject can be compressed by combining data within contiguous slots ofthe object into a single compression group. In this way, compression ofthe current snapshot maintained by the computing device is preservedwhen the current snapshot is stored in the object store as the objectcorresponding to a copy of the current snapshot.

The object, comprising the data of the deduplicated set of changed blocknumbers, is transmitted to the object store for storage as a new copiedsnapshot that is a copy of the current snapshot maintained by thecomputing device. The object is stored as a logical copy of the currentsnapshot. Also, additional compression is applied to this logical data,and information used to uncompress the logical data is stored in theobject header. Further, the object is maintained as an independentlogical representation of the current snapshot, such that copied data,copied from the current snapshot, is accessible through the objectwithout having to reference other logical copies of other copiedsnapshots stored in other objects within the object store. Once theobject is stored within the object store, the mapping metafile and/orthe overflow mapping metafile is updated with entries for thededuplicated set of changed block numbers based upon receiving anacknowledgment of the object being stored by the object store. An entrywill map a changed block number to a cloud block number of a slot withinwhich data of the changed block number is stored in the object.

As provided herein, an object file system is provided that is used tostore, retrieve, and manage objects within an object store, such as acloud computing environment. The object file system is capable ofrepresenting data in the object store in a structured format. It may beappreciated that any type of data (e.g., a file, a directory, an image,a storage virtual machine, a logical unit number (LUN), applicationdata, backup data, metadata, database data, a virtual machine disk,etc.) residing in any type of computing device (e.g., a computer, alaptop, a wearable device, a tablet, a storage controller, a node, anon-premise server, a virtual machine, another object store or cloudcomputing environment, a hybrid storage environment, data already storedwithin the object store, etc.) using any type of file system can bestored into objects for storage within the object store. This allows thedata to be represented as a file system so that the data of the objectscan be accessed and mounted on-demand by remote computing devices. Thisalso provides a high degree of flexibility in being able to access datafrom the object store, a cloud service, and/or a network file system foranalytics or data access on an on-demand basis. The object file systemis able to represent snapshots in the object store, and provides theability to access snapshot data universally for whomever has access toan object format of the object file system. Snapshots in the objectstore are self-representing, and the object file system provides accessto a complete snapshot copy without having to access other snapshots.

The object file system provides the ability to store any number ofsnapshots in the object store so that cold data (e.g., infrequentlyaccessed data) can be stored for long periods of time in a costeffective manner, such as in the cloud. The object file system storesdata within relatively larger objects to reduce cost. Representation ofdata in the object store is complete, such that all data and requiredcontainer properties can be independently recovered from the objectstore. The object file system format ensures that access is consistentand is not affected by eventual consistent nature of underlying cloudinfrastructure.

The object file system provides version neutrality. Changes to on-premmetadata versions provide little impact on the representation of data inthe object store. This allow data to be stored from multiple versions ofon-prem over time, and the ability to access data in the object storewithout much version management. The object file system provides anobject format that is conducive to garbage collection for freeingobjects (e.g., free slots and/or objects storing data of a deletesnapshot), such as where a lower granularity of data can be garbagecollected such as at a per snapshot deletion level.

In an embodiment, snapshots of data, such as of a primary volume,maintained by a computing device (e.g., a node, storage controller, orother on-prem device that is remote to the object store) can be createdby the computing device. The snapshots can be stored in the object storeindependent of the primary volume and can be retained for any durationof time. Data can be restored from the snapshots without dependency onthe primary volume. The snapshot copies in the object store can be usedfor load distribution, development testing, virus scans, analytics, etc.Because the snapshot copies (e.g., snapshot data stored within objects)are independent of the primary volume at the computing device, suchoperations can be performed without impacting performance of thecomputing device.

A snapshot is frozen in time representation of a filesystem. All thenecessary information may be organized as files. All the blocks of thefile system may be stitched together using cloud block numbers (e.g., acloud block number comprises a sequence number of an object and a slotnumber of a slot within that object) and the file will be represented bya data structure (e.g., represented in a tree format of a treestructure) when stored into the object store within one or more objects.Using cloud block numbers, a next node within the tree structure can beidentified for traversing the tree structure to locate a noderepresenting data to be accessed. The block of the data may be packedinto bigger objects to be cloud storage friendly, where blocks arestored into slots of a bigger object that is then stored within theobject store. All the indirections (pointers) to reach leaf nodes of afile (e.g., user data such as file data is represented by leaf nodeswithin the tree structure) may be normalized and may be versionindependent. Every snapshot may be a completely independent copy and anydata for a snapshot can be located by walking the object file system.While doing incremental snapshot copy, changed blocks between twosnapshots may be copied to the object store, and unchanged blocks willbe shared with previous snapshots as opposed to being redundantly storedin the object store. In this way, deduplication is provided for andbetween snapshot data stored within objects of the object store. As willbe described later, an embodiment of a snapshot file system in theobject store is illustrated by FIG. 4B.

Cloud block numbers are used to uniquely represent data (e.g., a block'sworth of information from the computing device) in the object store atany point in time. A cloud block number is used to derive an object name(e.g., a sequence number) and an index (a particular slot) within theobject. An object format, used by the object file system to formatobjects, allows for sharing of cloud blocks. This provides for storagespace efficiency across snapshots so that deduplication and compressionused by the computing device will be preserved. Additional compressionis applied before writing objects to the object store and information todecompress the data is kept in the object header.

Similar to data (e.g., a file, directory, or other data stored by thecomputing device), metadata can be stored into objects. Metadata isnormalized so that the restoration of data using the metadata from anobject to a remote computing device will be version independent. Thatis, snapshot data at the computing device can be stored into objects ina version neutral manner. Snapshots can be mounted and traversedindependent of one another, and thus data within an object isrepresented as a file system, such as according to the tree structure.The format of non-leaf nodes of the tree structure (e.g., indirects suchas pointers to other non-leaf nodes or to leaf nodes of user data) canchange over time. In this way, physical data is converted into a versionindependent format as part of normalization. Denormalization may beperformed while retrieving data from the objects, such as to restore asnapshot. In an example of normalization, a slot header in an object hasa flag that can be set to indicate that a slot comprises normalizedcontent. Each slot of the object is independently represented. Slot datamay comprise version data. The slot data may specify a number of entrieswithin the object and an entry size so that starting offsets of a nextentry can be calculated from the entry size of a current entry.

In an embodiment, denormalization of a first version of data/metadata(e.g., a prior version) can be retrieved from data backed up in anobject according to a second version (e.g., a future version). In anexample, if the future version added a new field, then duringdenormalization, the new field is skipped over. Denormalization of afuture version can be retrieved from data backed up in an objectaccording to a prior version. A version indicator in the slot data canbe used to determine how of an entry is to be read and interpreted, andany missing fields will be set to default values.

In an embodiment of the object format of objects stored within theobject store, relatively larger objects will be stored in the objectstore. As will be described later, an embodiment of an object isillustrated by FIG. 4C. An object comprises an object header followed bydata blocks (slots). The object header has a static array of slotcontext comprising information used to access data for slots. Each slotcan represent any length of logical data (e.g., a slot is a base unit ofdata of the object file system of the object store). Since data blocksfor metadata are normalized, a slot can represent any length of logicaldata. Data within the slots can be compressed into compression groups,and a slot will comprise enough information for how to decompress andreturn data of the slot.

In an embodiment, storage efficiency provided by the computing device ispreserved within the object store. A volume copied from the computingdevice into objects of the object store is maintained in the objectstore as an independent logical representation of the volume. Anygranularity of data can be represented, such as a directory, a qtree, afile, or other data container. A mapping metafile (a VMAP) is used tomap virtual block IDs/names (e.g., a virtual volume block number, ahash, a compression group name, or any other set of names of acollection of data used by the computing device) to cloud block numbersin the object store. This mapping metafile can be used to trackduplicate data per data container for storage efficiency.

The mapping metafile enables duplicate data detection of duplicate data,such as a duplicate block or a compression group (e.g., a compressedgroup of blocks/slots within an object). The mapping metafile is used topreserve sharing of data within and across multiple snapshots storedwithin objects in the object store. The mapping metafile is used forsharing of groups of data represented by a unique name. The mappingmetafile is used to populate indirect blocks with corresponding cloudblock numbers for children nodes (e.g., compressed or non-compressed).The mapping metafile is used to help a garbage collector make decisionson what cloud block numbers can be freed from the object store when acorresponding snapshot is deleted by the computing device. The mappingmetafile is updated during a snapshot copy operation to store snapshotdata from the computing device into objects within the object store. Anoverflow mapping metafile can also be used, such as to represent entrieswith base key collision. The overflow mapping metafile will supportvariable length key and payload in order to optimize a key sizeaccording to a type of entry in the overflow mapping metafile.

The mapping metafile may be indexed by virtual volume block numbers orstarting virtual volume block numbers of a compression group. An entrywithin the mapping metafile may comprise a virtual volume block numberas a key, a cloud block number, an indication of whether the cloud blocknumber is the start of a compression group, a compression indicator, anindicator as to whether additional information is stored in the overflowmapping metafile, a logical length of the compression group, a physicallength of the compression group, etc. Entries are removed/invalidatedfrom the mapping metafile if corresponding virtual volume block numbersare freed by the computing device, such as when a snapshot is deleted bythe computing device.

The data structure, such as the tree structure, is used to representdata within an object. Each node of the tree structure is represented bya cloud block number. The key to the tree structure may uniquelyidentify uncompressed virtual volume block numbers, a contiguous ornon-contiguous compression group represented by virtual volume blocknumbers associated with such, and/or an entry for non-starting virtualvolume block numbers of the compression group to a starting virtualvolume block number of the compression group. A key will comprise avirtual volume block number, a physical length of a compression group,an indicator as to whether the entry represents a start of thecompression group, and/or a variable length array of virtual volumeblock numbers of either non-starting virtual volume block numbers or thestarting virtual volume block number (if uncompressed then this is fieldis not used). The payload will comprise cloud block numbers and/or flagscorresponding to entries within the mapping metafile.

Before transferring objects to the object store for an incrementalsnapshot, the mapping metafile is processed to clear any stale entries.This is to ensure that a stale virtual volume block number orcompression group name is not reused for sharing (deduplication). Inparticular, between two snapshots, all virtual volume block numberstransitioning from a 1 to 0 (to indicate that the virtual volume blocknumbers are no longer used) in a snapshot to be copied to the objectstore in one or more objects are identified. Entries within the mappingmetafile for these virtual volume block numbers transitioning from a 1to 0 are removed from the mapping metafile. In this way, all entriesusing these virtual volume block numbers are invalidated.

As part of copying a snapshot to the object store, changed data andindirections for accessing the changed data are transferred (or all datafor initialization). In particular, changed user data of the computingdevice is traversed through buftrees using a snapdiff operation todetermine a data difference between two snapshots. Logical(uncompressed) data is read and populated into objects and associatedwith cloud block numbers. To preserve storage efficiency, a mapping froma unique name representing the logical data (e.g., virtual volume blocknumber or a compression group name for compressed data) to a cloud blocknumber (e.g., of a slot within which the logical data is stored) isrecorded in the mapping metafile. Lookups to the mapping metafile willbe performed to ensure only a single copy of changed blocks are copiedto the object store. Metadata is normalized for version independency andstored into objects. Indirects (non-leaf nodes) are stored in the objectto refer to unchanged old cloud blocks and changed new cloud blocks arestored in the object, which provides a complete view of user data andmetadata for each snapshot. Inodes are written to the object store whilepushing changed inofile blocks to the object store. Each inode entrywithin an inofile is normalized to represent a version independent inodeformat. Each inode will have a list of next level of indirect blocks(e.g., non-leaf nodes of the tree structure storing indirects/pointersto other nodes). Snapinfo objects comprise snapshot specificinformation. A snapinfo object of a snapshot has a pointer to a root ofa snapshot logical file system. A root object for each primary volume(e.g., a primary volume for which a snapshot is captured) is copied tothe object store. Each snapshot is associated with an object ID(sequence number) map that tracks which objects are in use in a snapshot(e.g., which objects comprise data of the snapshot) and is subsequentlyused for garbage collection in the future when a particular snapshot isdeleted.

In an embodiment of data access and restoration, the tree formatrepresents an object file system (a cloud file system) that can bemounted and/or traversed from any remote device utilizing APIs using athin layer orchestrating between client requests and object file systemtraversal. A remote device provides an entry point to the object treeusing a universal identifier (UUID) that is a common identifier for allobject names for a volume (or container). A rel root object is derivedfrom the UUID, which has pointers (names) to next level snapinfoobjects. If a user is browsing a snapshot, a snapshot snapinfo is lookedup within snapinfo objects. If no snapshot is provided, then latestsnapshot info is used. The snapshot info has cloud block numbers for aninode file. The inode file is read from the object store using the cloudblock number and an inode within the inode file is read by traversingthe inode file's tree structure. Each level including the inode has acloud block number for a next level until a leaf node (a level 0 blockof data) is read. Thus, the inode for the file of interest is obtained,and the file's tree structure is traversed by looking up cloud blocknumber for a next level of the tree structure (e.g., a cloud blocknumber from a level 1 is used to access the level 0 block) until therequired data is read. Object headers and higher level indirects arecached to reduce the amount of access to the object store. Additionally,more data may be read from the object store than needed to benefit fromlocality for caching. Data access can be used to restore a complete copyof a snapshot, part of a snapshot (e.g., a single file or directory), ormetadata.

In an embodiment of read/write cloning, a volume or file, backed from asnapshot in the object store, is created. Read access will use a dataaccess path through a tree structure. At a high level, write access willread the required data from the object store (e.g., user data and alllevels of the file/volume tree that are part of user data modificationby a write operation). The blocks are modified and the modified contentis rewritten to the object store.

In an embodiment, defragmentation is provided for objects comprisingsnapshot copies in the object store and to prevent fragmented objectsfrom being sent to the object store during backup. Defragmentation ofobjects involves rewriting an object with only used data, which mayexclude unused/freed data no longer used by the computing device (e.g.,data of a deleted snapshot no longer referenced by other snapshots). Anobject can only be overwritten if used data is not changed. Objectsequence numbers are not reused. Only unused data can be freed, but useddata cannot be overwritten. Reads will ensure that slot header and dataare read from same object (timestamp checking). Reading data from theobject store involves reading the header info and then reading theactual data. If these two reads go to different objects (as determinedby timestamp comparison), then the read operation is failed and retried.

Defragmentation occurs when snapshots are deleted and objects could notbe freed because another snapshot still contains some reference to theobjects that would be freed (not all slots within these objects arefreed but some still comprise used data from other snapshots). A slotwithin an object can only be freed when all snapshots referring to thatslot are deleted (e.g., an oldest snapshot having the object in use suchthat younger snapshots do not reuse the freed slots). Also, ownershipcount can be persistently stored. When a snapshot is deleted, allobjects uniquely owned by that snapshot are freed, but objects presentin other snapshots (e.g., a next/subsequent snapshot) are not freed. Acount of such objects is stored with a next snapshot so that the nextsnapshot becomes the owner of those objects. Defragmentation is onlyperformed when a number of used slots in an object (an object refcount)is less than a threshold. If the number is below a second threshold,then further defragmentation is not performed. In order to identify usedslots and free slots, the file system in the snapshot is traversed and abitmap is constructed where a bit will be used to denote if a cloudblock is in use (a cloud block in-use bitmap). This map is used tocalculate the object refcount.

To perform defragmentation, the cloud block in-use map is prepared bywalking the cloud snapshot file system. This bitmap is walked togenerate an object refcount for the object. The object refcount ischecked to see if it is within a range to be defragmented. The object ischecked to see if the object is owned by the snapshot by comparing anobject ID map of a current and a previous snapshot. If the object isowned and is to be defragmented, then the cloud block in-use map is usedto find free slots and to rewrite the object to comprise data from usedslots and to exclude freed slots. The object header will be updatedaccordingly with new offsets.

Fragmentation may be mitigated. During backup, an object ID map iscreated to contain a bit for each object in use by the snapshot (e.g.,objects storing snapshot data of the snapshot). The mapping metafile(VMAP) is walked to create the object ID map. An object reference mapcan be created to store a count of a number of cloud blocks in use inthat object. If the count is below a threshold, then data of the usedblocks can be rewritten in a new object.

For each primary volume copied to the object store, there is a rootobject having a name starting with a prefix followed by a destinationend point name and UUID. The root object is written during a concludephase. Another copy for the root object is maintained with a unique nameas a defense to eventual consistency, and will have a generation numberappended to the name. A relationship state metafile will be updatedbefore the root object info is updated. The root object has a header,root info, and bookkeeping information. A snapshot info is an objectcontaining snapshot specific information, and is written during aconclude phase of a backup operation. Each object will have its ownunique sequence number, which is generated automatically.

To provide for managing objects within an object store using an objectfile system, FIG. 1 illustrates an embodiment of a clustered networkenvironment 100 or a network storage environment. It may be appreciated,however, that the techniques, etc. described herein may be implementedwithin the clustered network environment 100, a non-cluster networkenvironment, and/or a variety of other computing environments, such as adesktop computing environment. That is, the instant disclosure,including the scope of the appended claims, is not meant to be limitedto the examples provided herein. It will be appreciated that where thesame or similar components, elements, features, items, modules, etc. areillustrated in later figures but were previously discussed with regardto prior figures, that a similar (e.g., redundant) discussion of thesame may be omitted when describing the subsequent figures (e.g., forpurposes of simplicity and ease of understanding).

FIG. 1 is a block diagram illustrating the clustered network environment100 that may implement at least some embodiments of the techniquesand/or systems described herein. The clustered network environment 100comprises data storage systems 102 and 104 that are coupled over acluster fabric 106, such as a computing network embodied as a privateInfiniband, Fibre Channel (FC), or Ethernet network facilitatingcommunication between the data storage systems 102 and 104 (and one ormore modules, component, etc. therein, such as, nodes 116 and 118, forexample). It will be appreciated that while two data storage systems 102and 104 and two nodes 116 and 118 are illustrated in FIG. 1, that anysuitable number of such components is contemplated. In an example, nodes116, 118 comprise storage controllers (e.g., node 116 may comprise aprimary or local storage controller and node 118 may comprise asecondary or remote storage controller) that provide client devices,such as host devices 108, 110, with access to data stored within datastorage devices 128, 130. Similarly, unless specifically providedotherwise herein, the same is true for other modules, elements,features, items, etc. referenced herein and/or illustrated in theaccompanying drawings. That is, a particular number of components,modules, elements, features, items, etc. disclosed herein is not meantto be interpreted in a limiting manner.

It will be further appreciated that clustered networks are not limitedto any particular geographic areas and can be clustered locally and/orremotely. Thus, In an embodiment a clustered network can be distributedover a plurality of storage systems and/or nodes located in a pluralityof geographic locations; while In an embodiment a clustered network caninclude data storage systems (e.g., 102, 104) residing in a samegeographic location (e.g., in a single onsite rack of data storagedevices).

In the illustrated example, one or more host devices 108, 110 which maycomprise, for example, client devices, personal computers (PCs),computing devices used for storage (e.g., storage servers), and othercomputers or peripheral devices (e.g., printers), are coupled to therespective data storage systems 102, 104 by storage network connections112, 114. Network connection may comprise a local area network (LAN) orwide area network (WAN), for example, that utilizes Network AttachedStorage (NAS) protocols, such as a Common Internet File System (CIFS)protocol or a Network File System (NFS) protocol to exchange datapackets, a Storage Area Network (SAN) protocol, such as Small ComputerSystem Interface (SCSI) or Fiber Channel Protocol (FCP), an objectprotocol, such as S3, etc. Illustratively, the host devices 108, 110 maybe general-purpose computers running applications, and may interact withthe data storage systems 102, 104 using a client/server model forexchange of information. That is, the host device may request data fromthe data storage system (e.g., data on a storage device managed by anetwork storage control configured to process I/O commands issued by thehost device for the storage device), and the data storage system mayreturn results of the request to the host device via one or more storagenetwork connections 112, 114.

The nodes 116, 118 on clustered data storage systems 102, 104 cancomprise network or host nodes that are interconnected as a cluster toprovide data storage and management services, such as to an enterprisehaving remote locations, cloud storage (e.g., a storage endpoint may bestored within a data cloud), etc., for example. Such a node in theclustered network environment 100 can be a device attached to thenetwork as a connection point, redistribution point or communicationendpoint, for example. A node may be capable of sending, receiving,and/or forwarding information over a network communications channel, andcould comprise any device that meets any or all of these criteria. Oneexample of a node may be a data storage and management server attachedto a network, where the server can comprise a general purpose computeror a computing device particularly configured to operate as a server ina data storage and management system.

In an example, a first cluster of nodes such as the nodes 116, 118(e.g., a first set of storage controllers configured to provide accessto a first storage aggregate comprising a first logical grouping of oneor more storage devices) may be located on a first storage site. Asecond cluster of nodes, not illustrated, may be located at a secondstorage site (e.g., a second set of storage controllers configured toprovide access to a second storage aggregate comprising a second logicalgrouping of one or more storage devices). The first cluster of nodes andthe second cluster of nodes may be configured according to a disasterrecovery configuration where a surviving cluster of nodes providesswitchover access to storage devices of a disaster cluster of nodes inthe event a disaster occurs at a disaster storage site comprising thedisaster cluster of nodes (e.g., the first cluster of nodes providesclient devices with switchover data access to storage devices of thesecond storage aggregate in the event a disaster occurs at the secondstorage site).

As illustrated in the clustered network environment 100, nodes 116, 118can comprise various functional components that coordinate to providedistributed storage architecture for the cluster. For example, the nodescan comprise network modules 120, 122 and disk modules 124, 126. Networkmodules 120, 122 can be configured to allow the nodes 116, 118 (e.g.,network storage controllers) to connect with host devices 108, 110 overthe storage network connections 112, 114, for example, allowing the hostdevices 108, 110 to access data stored in the distributed storagesystem. Further, the network modules 120, 122 can provide connectionswith one or more other components through the cluster fabric 106. Forexample, in FIG. 1, the network module 120 of node 116 can access asecond data storage device by sending a request through the disk module126 of node 118.

Disk modules 124, 126 can be configured to connect one or more datastorage devices 128, 130, such as disks or arrays of disks, flashmemory, or some other form of data storage, to the nodes 116, 118. Thenodes 116, 118 can be interconnected by the cluster fabric 106, forexample, allowing respective nodes in the cluster to access data on datastorage devices 128, 130 connected to different nodes in the cluster.Often, disk modules 124, 126 communicate with the data storage devices128, 130 according to the SAN protocol, such as SCSI or FCP, forexample. Thus, as seen from an operating system on nodes 116, 118, thedata storage devices 128, 130 can appear as locally attached to theoperating system. In this manner, different nodes 116, 118, etc. mayaccess data blocks through the operating system, rather than expresslyrequesting abstract files.

It should be appreciated that, while the clustered network environment100 illustrates an equal number of network and disk modules, otherembodiments may comprise a differing number of these modules. Forexample, there may be a plurality of network and disk modulesinterconnected in a cluster that does not have a one-to-onecorrespondence between the network and disk modules. That is, differentnodes can have a different number of network and disk modules, and thesame node can have a different number of network modules than diskmodules.

Further, a host device 108, 110 can be networked with the nodes 116, 118in the cluster, over the storage networking connections 112, 114. As anexample, respective host devices 108, 110 that are networked to acluster may request services (e.g., exchanging of information in theform of data packets) of nodes 116, 118 in the cluster, and the nodes116, 118 can return results of the requested services to the hostdevices 108, 110. In an embodiment, the host devices 108, 110 canexchange information with the network modules 120, 122 residing in thenodes 116, 118 (e.g., network hosts) in the data storage systems 102,104.

In an embodiment, the data storage devices 128, 130 comprise volumes132, which is an implementation of storage of information onto diskdrives or disk arrays or other storage (e.g., flash) as a file-systemfor data, for example. In an example, a disk array can include alltraditional hard drives, all flash drives, or a combination oftraditional hard drives and flash drives. Volumes can span a portion ofa disk, a collection of disks, or portions of disks, for example, andtypically define an overall logical arrangement of file storage on diskspace in the storage system. In an embodiment a volume can comprisestored data as one or more files that reside in a hierarchical directorystructure within the volume.

Volumes are typically configured in formats that may be associated withparticular storage systems, and respective volume formats typicallycomprise features that provide functionality to the volumes, such asproviding an ability for volumes to form clusters. For example, where afirst storage system may utilize a first format for their volumes, asecond storage system may utilize a second format for their volumes.

In the clustered network environment 100, the host devices 108, 110 canutilize the data storage systems 102, 104 to store and retrieve datafrom the volumes 132. In this embodiment, for example, the host device108 can send data packets to the network module 120 in the node 116within data storage system 102. The node 116 can forward the data to thedata storage device 128 using the disk module 124, where the datastorage device 128 comprises volume 132A. In this way, in this example,the host device can access the volume 132A, to store and/or retrievedata, using the data storage system 102 connected by the storage networkconnection 112. Further, in this embodiment, the host device 110 canexchange data with the network module 122 in the node 118 within thedata storage system 104 (e.g., which may be remote from the data storagesystem 102). The node 118 can forward the data to the data storagedevice 130 using the disk module 126, thereby accessing volume 1328associated with the data storage device 130.

It may be appreciated that incremental snapshot copy to object store maybe implemented within the clustered network environment 100, such aswhere nodes within the clustered network environment store data asobjects within a remote object store. It may be appreciated thatincremental snapshot copy to object store may be implemented for and/orbetween any type of computing environment, and may be transferrablebetween physical devices (e.g., node 116, node 118, a desktop computer,a tablet, a laptop, a wearable device, a mobile device, a storagedevice, a server, etc.) and/or a cloud computing environment (e.g.,remote to the clustered network environment 100).

FIG. 2 is an illustrative example of a data storage system 200 (e.g.,102, 104 in FIG. 1), providing further detail of an embodiment ofcomponents that may implement one or more of the techniques and/orsystems described herein. The data storage system 200 comprises a node202 (e.g., nodes 116, 118 in FIG. 1), and a data storage device 234(e.g., data storage devices 128, 130 in FIG. 1). The node 202 may be ageneral purpose computer, for example, or some other computing deviceparticularly configured to operate as a storage server. A host device205 (e.g., 108, 110 in FIG. 1) can be connected to the node 202 over anetwork 216, for example, to provide access to files and/or other datastored on the data storage device 234. In an example, the node 202comprises a storage controller that provides client devices, such as thehost device 205, with access to data stored within data storage device234.

The data storage device 234 can comprise mass storage devices, such asdisks 224, 226, 228 of a disk array 218, 220, 222. It will beappreciated that the techniques and systems, described herein, are notlimited by the example embodiment. For example, disks 224, 226, 228 maycomprise any type of mass storage devices, including but not limited tomagnetic disk drives, flash memory, and any other similar media adaptedto store information, including, for example, data (D) and/or parity (P)information.

The node 202 comprises one or more processors 204, a memory 206, anetwork adapter 210, a cluster access adapter 212, and a storage adapter214 interconnected by a system bus 242. The data storage system 200 alsoincludes an operating system 208 installed in the memory 206 of the node202 that can, for example, implement a Redundant Array of Independent(or Inexpensive) Disks (RAID) optimization technique to optimize areconstruction process of data of a failed disk in an array.

The operating system 208 can also manage communications for the datastorage system, and communications between other data storage systemsthat may be in a clustered network, such as attached to a cluster fabric215 (e.g., 106 in FIG. 1). Thus, the node 202, such as a network storagecontroller, can respond to host device requests to manage data on thedata storage device 234 (e.g., or additional clustered devices) inaccordance with these host device requests. The operating system 208 canoften establish one or more file systems on the data storage system 200,where a file system can include software code and data structures thatimplement a persistent hierarchical namespace of files and directories,for example. As an example, when a new data storage device (not shown)is added to a clustered network system, the operating system 208 isinformed where, in an existing directory tree, new files associated withthe new data storage device are to be stored. This is often referred toas “mounting” a file system.

In the example data storage system 200, memory 206 can include storagelocations that are addressable by the processors 204 and adapters 210,212, 214 for storing related software application code and datastructures. The processors 204 and adapters 210, 212, 214 may, forexample, include processing elements and/or logic circuitry configuredto execute the software code and manipulate the data structures. Theoperating system 208, portions of which are typically resident in thememory 206 and executed by the processing elements, functionallyorganizes the storage system by, among other things, invoking storageoperations in support of a file service implemented by the storagesystem. It will be apparent to those skilled in the art that otherprocessing and memory mechanisms, including various computer readablemedia, may be used for storing and/or executing application instructionspertaining to the techniques described herein. For example, theoperating system can also utilize one or more control files (not shown)to aid in the provisioning of virtual machines.

The network adapter 210 includes the mechanical, electrical andsignaling circuitry needed to connect the data storage system 200 to ahost device 205 over a network 216, which may comprise, among otherthings, a point-to-point connection or a shared medium, such as a localarea network. The host device 205 (e.g., 108, 110 of FIG. 1) may be ageneral-purpose computer configured to execute applications. Asdescribed above, the host device 205 may interact with the data storagesystem 200 in accordance with a client/host model of informationdelivery.

The storage adapter 214 cooperates with the operating system 208executing on the node 202 to access information requested by the hostdevice 205 (e.g., access data on a storage device managed by a networkstorage controller). The information may be stored on any type ofattached array of writeable media such as magnetic disk drives, flashmemory, and/or any other similar media adapted to store information. Inthe example data storage system 200, the information can be stored indata blocks on the disks 224, 226, 228. The storage adapter 214 caninclude input/output (I/O) interface circuitry that couples to the disksover an I/O interconnect arrangement, such as a storage area network(SAN) protocol (e.g., Small Computer System Interface (SCSI), iSCSI,hyperSCSI, Fiber Channel Protocol (FCP)). The information is retrievedby the storage adapter 214 and, if necessary, processed by the one ormore processors 204 (or the storage adapter 214 itself) prior to beingforwarded over the system bus 242 to the network adapter 210 (and/or thecluster access adapter 212 if sending to another node in the cluster)where the information is formatted into a data packet and returned tothe host device 205 over the network 216 (and/or returned to anothernode attached to the cluster over the cluster fabric 215).

In an embodiment, storage of information on disk arrays 218, 220, 222can be implemented as one or more storage volumes 230, 232 that arecomprised of a cluster of disks 224, 226, 228 defining an overalllogical arrangement of disk space. The disks 224, 226, 228 that compriseone or more volumes are typically organized as one or more groups ofRAIDs. As an example, volume 230 comprises an aggregate of disk arrays218 and 220, which comprise the cluster of disks 224 and 226.

In an embodiment, to facilitate access to disks 224, 226, 228, theoperating system 208 may implement a file system (e.g., write anywherefile system) that logically organizes the information as a hierarchicalstructure of directories and files on the disks. In this embodiment,respective files may be implemented as a set of disk blocks configuredto store information, whereas directories may be implemented asspecially formatted files in which information about other files anddirectories are stored.

Whatever the underlying physical configuration within this data storagesystem 200, data can be stored as files within physical and/or virtualvolumes, which can be associated with respective volume identifiers,such as file system identifiers (FSIDs), which can be 32-bits in lengthin one example.

A physical volume corresponds to at least a portion of physical storagedevices whose address, addressable space, location, etc. doesn't change,such as at least some of one or more data storage devices 234 (e.g., aRedundant Array of Independent (or Inexpensive) Disks (RAID system)).Typically the location of the physical volume doesn't change in that the(range of) address(es) used to access it generally remains constant.

A virtual volume, in contrast, is stored over an aggregate of disparateportions of different physical storage devices. The virtual volume maybe a collection of different available portions of different physicalstorage device locations, such as some available space from each of thedisks 224, 226, and/or 228. It will be appreciated that since a virtualvolume is not “tied” to any one particular storage device, a virtualvolume can be said to include a layer of abstraction or virtualization,which allows it to be resized and/or flexible in some regards.

Further, a virtual volume can include one or more logical unit numbers(LUNs) 238, directories 236, Qtrees 235, and files 240. Among otherthings, these features, but more particularly LUNS, allow the disparatememory locations within which data is stored to be identified, forexample, and grouped as data storage unit. As such, the LUNs 238 may becharacterized as constituting a virtual disk or drive upon which datawithin the virtual volume is stored within the aggregate. For example,LUNs are often referred to as virtual drives, such that they emulate ahard drive from a general purpose computer, while they actually comprisedata blocks stored in various parts of a volume.

In an embodiment, one or more data storage devices 234 can have one ormore physical ports, wherein each physical port can be assigned a targetaddress (e.g., SCSI target address). To represent respective volumesstored on a data storage device, a target address on the data storagedevice can be used to identify one or more LUNs 238. Thus, for example,when the node 202 connects to a volume 230, 232 through the storageadapter 214, a connection between the node 202 and the one or more LUNs238 underlying the volume is created.

In an embodiment, respective target addresses can identify multipleLUNs, such that a target address can represent multiple volumes. The I/Ointerface, which can be implemented as circuitry and/or software in thestorage adapter 214 or as executable code residing in memory 206 andexecuted by the processors 204, for example, can connect to volume 230by using one or more addresses that identify the one or more LUNs 238.

It may be appreciated that incremental snapshot copy to object store maybe implemented for the data storage system 200. It may be appreciatedthat incremental snapshot copy to object store may be implemented forand/or between any type of computing environment, and may betransferrable between physical devices (e.g., node 202, host device 205,a desktop computer, a tablet, a laptop, a wearable device, a mobiledevice, a storage device, a server, etc.) and/or a cloud computingenvironment (e.g., remote to the node 202 and/or the host device 205).

One embodiment of incremental snapshot copy to object store isillustrated by an exemplary method 300 of FIG. 3 and further describedin conjunction with system 400 of FIGS. 4A-4D. A computing device 402may comprise a node, a storage controller, a storage service, anon-premises computing device, a storage virtual machine, or any otherhardware or software (e.g., software as a service). The computing device402 may store data within storage devices (primary storage) managed bythe computing device 402. The computing device 402 may provide clientdevices with access to the data, such as by processing read and writeoperations from the client devices. The computing device 402 may createsnapshots of the data, such as a snapshot of a file system of a volumeaccessible to the client devices through the computing device 402. Forexample, the computing device 402 may create a first snapshot 404 of thefile system at a first point in time, a second snapshot 406 of the filesystem at a second point in time subsequent the first point in time,etc.

The computing device 402 may be configured to communicate with an objectstore 410 over a network. The object store 410 may comprise a cloudcomputing environment remote to the computing device 402, and isaccessible to the computing device 402 over a network. The object store410 may provide scalable cost effective storage for the computing device402. Accordingly, the computing device 402 may incrementally copysnapshots of the primary storage of the computing device 402 intoobjects for storage in the object store 410 as copied snapshots. Forexample, data of the first snapshot 404 may be stored into slots a firstobject 412, and the first object 412 is then stored into the objectstore 410 as a first copied snapshot.

The computing device 402 is able to utilize an object file system andobject format to store data into objects within the object store 410.For example, data, maintained by the computing device 402, is storedinto a plurality of slots of an object. Each slot represents a base unitof data of the object file system defined for the object store 410. Forexample, the object comprises 1024 or any other number of slots, whereineach slot comprises 4 kb of data or any other amount of data. It may beappreciated that objects may comprise any number of slots of any size.Snapshot data, user data, directory blocks, metadata, and/or inofileblocks of an inofile comprising per inode metadata is stored into theslots of the object. In an example, snapshot data, of a snapshot createdby the computing device 402 of the file system maintained by thecomputing device 402, is stored into the object (e.g., snapshot data ofthe first snapshot 404 is stored into the first object 412). Forexample, the object may be maintained as an independent logicalrepresentation of the snapshot, such that data of the snapshot isaccessible through the object without having to reference other logicalcopies of other snapshots stored within objects of the object store 410,according to some embodiments. In an example, the data is converted fromphysical data into a version independent format for storage within theobject.

In an example, the object is created to comprise data in a compressedstate corresponding to compression of the data within the primarystorage of the computing device 402. In this way, compression used bythe computing device 402 to store the data is retained within the objectfor storage within the object store 410. The object may be assigned aunique sequence number. Each object within the object store 410 isassigned unique sequence numbers.

An object header may be created for the object. The object headercomprises a slot context for slots within the object. The slot contextmay comprise information relating to a type of compression used forcompressing data within the object (if any compression is used), a startoffset of a slot, a logical data length, a compressed data length, etc.The slot context may be used to access compressed data stored within theobject. The object header comprises various information, such as aversion identifier, a header checksum, a length of the object, a slotcontext, and/or other information used to access and manage datapopulated into the slots of the object. The slot context comprisesvarious information about the slots, such as a compression type of aslot (e.g., a type of compression used to compress data of slots into acompression group or an indicator that the slot does not comprisecompressed data), a start offset of the slot within the object (e.g., aslot identifier multiplied by a slot size, such as 4 kb), a logical datalength of the slot (e.g., 4 kb), a compressed length (e.g., 0 ifuncompressed), an index of the slot within a compression group ofmultiple slots (e.g., 0 if uncompressed), a logical data checksum, etc.

A mapping metafile 408 (a VMAP) is maintained for the object. Themapping metafile 408 maps block numbers of primary storage of thecomputing device 402 (e.g., virtual volume block numbers of the datastored into slots of the object) to cloud block numbers of nodes of atree structure representing portions of the data stored within the slotsof the object. As will be described later, the objects within the objectstore 410 may be deduplicated with respect to one another (e.g., theobject is deduplicated with respect to other objects using the mappingmetafile 480 as part of being stored into the object store 410) andretain compression used by the computing device 402 for storing thesnapshots within the primary storage.

In an embodiment, the mapping metafile 408 and/or an overflow mappingmetafile are used to facilitate the copying of the snapshots to theobject store 410 in a manner that preserves deduplication andcompression, logically represents the snapshots as fully independentsnapshots, and provides additional compression. In particular, themapping metafile 408 is populated with entries for block numbers (e.g.,virtual volume block numbers, physical volume block numbers, etc. usedby the computing device 402 to reference data such as snapshot datastored by the computing device 402) of the snapshots maintained by thecomputing device 402 and copied into the objects of the object store 410as copied snapshots. An entry within the mapping metafile 408 ispopulated with a mapping between a block number of data within asnapshot at the computing device 402 (e.g., a virtual volume blocknumber) and a cloud block number (e.g., a cloud physical volume blocknumber) of a slot within an object into which the data was copied whenthe snapshot was copied to the object store 410 as a copied snapshot.The entry within the mapping metafile 408 is populated with acompression indicator to indicate whether data of the block number iscompressed or not (e.g., a bit set to a first value to indicate acompressed virtual volume block number and set to a second value toindicate a non-compressed virtual volume block number).

The entry within the mapping metafile 408 is populated with acompression group start indicator to indicate whether the block numberis a starting block number for a compression group of a plurality ofblock numbers of compressed data blocks. The entry within the mappingmetafile 408 may be populated with a logical length of an extentassociated with the block number. The entry within the mapping metafile408 may be populated with a physical length of the extent associatedwith the block number.

The entry within the mapping metafile 408 is populated with an overflowindicator to indicate whether the data block has an overflow entrywithin the overflow mapping metafile. The overflow mapping metafile maycomprise a V+ tree, such as a special B+ tree with support for variablelength key and payload so a key can be sized according to a type ofentry being stored for optimization. The key uniquely represents alltypes of entries associated with a block number (a virtual volume blocknumber). The key may comprise a block number field (e.g., the virtualvolume block number of a data block represented by the block number or astarting virtual volume block number of a first data block of acompression group comprising the data block), a physical length of anextent of the data block, if the corresponding entry is a start of acompression group, and other block numbers of blocks within thecompression group. The payload is a cloud block number (a cloud physicalvolume block number).

The mapping metafile 408 and/or the overflow mapping metafile may beindexed by block numbers of the primary storage (e.g., virtual volumeblock numbers of snapshots stored by the computing device 402 within theprimary storage, which are copied to the object store 410 as copiedsnapshots). In an example, the block numbers may correspond to virtualvolume block numbers of data of the snapshots stored by the computingdevice 402 within the primary storage. In an example, a block numbercorresponds to a starting virtual volume block number of an extent of acompression group.

The mapping metafile 408 and/or the overflow mapping metafile ismaintained according to a first rule specifying that the mappingmetafile 408 and/or the overflow mapping metafile represent acomprehensive set of cloud block numbers corresponding to a latestsnapshot copied to the object store 410. The mapping metafile 408 and/orthe overflow mapping metafile is maintained according to a second rulespecifying that entries within the mapping metafile 408 and/or theoverflow mapping metafile are invalidated based upon any block number inthe entries being freed by the computing device 402.

A determination is made that a current snapshot, such as the secondsnapshot 406, is to be copied to the object store 410 as a copied secondsnapshot whose data is stored within a second object 418. The mappingmetafile 408 and/or the overflow mapping metafile is used to determinewhat data of the current snapshot is to be copied to the object store410 and what data already exists within the object store 410 so thatonly data not already within the object store 410 is transmitted to theobject store 410 for storage within the second object 418.

Upon determining that the current snapshot is to be copied to the objectstore 410, an invalidation phase is performed. At 302, a list ofdeallocated block numbers 411 of primary storage of the computing device402 (e.g., virtual volume block numbers, of the file system of whichsnapshots are created, that are no longer being actively used to storein-use data by the computing device 402) are determined, as illustratedby FIG. 4B. The list of deallocated block numbers 411 is determinedbased upon a difference between two snapshots of the primary storage(e.g., a difference between a base snapshot and an incremental snapshotof the file system), such as between the first snapshot 404 alreadycopied to the object store 410 and the second snapshot 406 that is to becopied to the object store 410. As part of the invalidation phase,entries for the list of deallocated block numbers 411 are removed fromthe mapping metafile 408 and/or the overflow mapping metafile, at 304.

This invalidation phase is performed to remove entries within themapping metafile 408 that are no longer valid due to the entries mappingdata no longer referenced by the computing device 4102, such as by thecurrent snapshot (e.g., the second snapshot 406). In particular, given adeallocated block's virtual volume block number, all entries within themapping metafile 408 and/or the overflow mapping metafile are identifiedand removed.

At 306, after the invalidation phase, a list of changed block numbers414 corresponding to changes between the current snapshot of the primarystorage being copied to the object store 410 and a prior copied snapshotalready copied from the primary storage to the object store 410 isdetermined (e.g., a delta between the first snapshot 404 and the secondsnapshot 406), as illustrated by FIG. 4C. The mapping metafile 408 isevaluated using the list of changed block numbers 414 to identify adeduplicated set of changed block numbers 416 without entries within themapping metafile 408, as illustrated by FIG. 4D. The deduplicated set ofchanged block numbers correspond to data, of the current snapshot (e.g.,the second snapshot 406), not yet stored within the object store 410.

That is, the mapping metafile 408, after the invalidation phase,corresponds to data already stored within the object store 410 (e.g.,the mapping metafile 408 maps block numbers of the primary storage tocloud block numbers of data currently stored within the object store410). The list of changed block numbers 414 correspond to differences(e.g., delta data) between the first snapshot 404 and the secondsnapshot 406 (e.g., new data written to the file system after the firstsnapshot 404 was created, which existed in the file system when thesecond snapshot 406 of the file system was created). However, some ofthe delta data may already be stored within the object store 410. Thus,the list of changed block numbers 414 of the delta data are used todetermine whether there are corresponding entries within the mappingmetafile 408 mapping the changed block numbers to cloud block numbers ofdata already stored within the object store 410. If a changed blocknumber is mapping within the mapping metafile 408 to a cloud blocknumber, then the delta data of the changed block number is alreadywithin the object store 410 and thus the delta data is not includedwithin the second object 418. Instead, merely a reference is used inplace of the delta data. If a changed block number is not mapped withinthe mapping metafile 408 to any cloud block number, then delta data ofthe changed block number is included within the second object 418because the delta data is not already stored within the object store410. In this way, the deduplicate set of changed block numbers 416 ofdelta data not already stored within the object store 410 is identified.

The second object 418 is created to store data of the deduplicated setof changed block numbers 416 (e.g., data not already stored within theobject store 410, and thus the second object 418 is deduplicated withrespect to other data already stored within the object store 410 becausemerely references to the already stored data are used instead ofduplicate copies of the data being stored within the second object 418).The second object 418 comprises a plurality of slots, such as 1024 orany other number of slots. The data of the deduplicated set of changedblock numbers 416 is stored into the slots of the second object 418. Anobject header is updated with metadata describing the slots. In anexample, the second object 418 is created to comprise the data in acompressed state corresponding to compression of the data in the primarystorage. The second object 418 can be compressed by combining datawithin contiguous slots of the second object 418 into a singlecompression group. In this way, compression of the current snapshot(e.g., the second snapshot 406) maintained by the computing device 402is preserved when the current snapshot is stored in the object store 410as the second object 418 corresponding to a copy of the currentsnapshot.

The second object 418, comprising the data of the deduplicated set ofchanged block numbers 416, is transmitted to the object store 410 forstorage as a new copied snapshot that is a copy of the current snapshotmaintained by the computing device 402. The second object 418 is storedas a logical copy of the current snapshot. Also, additional compressionmay be applied to this logical data, and information used to uncompressthe logical data is stored in the object header. Further, the secondobject 418 is maintained as an independent logical representation of thecurrent snapshot, such that copied data, copied from the currentsnapshot, is accessible through the second object 418 without having toreference other logical copies of other copied snapshots stored in otherobjects within the object store 410, in some embodiments. Once thesecond object 418 is stored within the object store 410, the mappingmetafile 408 and/or the overflow mapping metafile is updated withentries for the deduplicated set of changed block numbers 416 based uponreceiving an acknowledgment of the second object 418 being stored by theobject store 410, at 312. An entry will map a changed block number to acloud block number of a slot within which data of the changed blocknumber is stored in the second object 418.

Still another embodiment involves a computer-readable medium 500comprising processor-executable instructions configured to implement oneor more of the techniques presented herein. An example embodiment of acomputer-readable medium or a computer-readable device that is devisedin these ways is illustrated in FIG. 5, wherein the implementationcomprises a computer-readable medium 508, such as a compactdisc-recordable (CD-R), a digital versatile disc-recordable (DVD-R),flash drive, a platter of a hard disk drive, etc., on which is encodedcomputer-readable data 506. This computer-readable data 506, such asbinary data comprising at least one of a zero or a one, in turncomprises a processor-executable computer instructions 504 configured tooperate according to one or more of the principles set forth herein. Insome embodiments, the processor-executable computer instructions 504 areconfigured to perform a method 502, such as at least some of theexemplary method 300 of FIG. 3, for example. In some embodiments, theprocessor-executable computer instructions 504 are configured toimplement a system, such as at least some of the exemplary system 400 ofFIGS. 4A-4B, for example. Many such computer-readable media arecontemplated to operate in accordance with the techniques presentedherein.

FIG. 6 is a diagram illustrating an example operating environment 600 inwhich an embodiment of the techniques described herein may beimplemented. In one example, the techniques described herein may beimplemented within a client device 628, such as a laptop, tablet,personal computer, mobile device, wearable device, etc. In anotherexample, the techniques described herein may be implemented within astorage controller 630, such as a node configured to manage the storageand access to data on behalf of the client device 628 and/or otherclient devices. In another example, the techniques described herein maybe implemented within a distributed computing platform 602 such as acloud computing environment (e.g., a cloud storage environment, amulti-tenant platform, etc.) configured to manage the storage and accessto data on behalf of the client device 628 and/or other client devices.

In yet another example, at least some of the techniques described hereinare implemented across one or more of the client device 628, the storagecontroller 630, and the distributed computing platform 602. For example,the client device 628 may transmit operations, such as data operationsto read data and write data and metadata operations (e.g., a create fileoperation, a rename directory operation, a resize operation, a setattribute operation, etc.), over a network 626 to the storage controller630 for implementation by the storage controller 630 upon storage. Thestorage controller 630 may store data associated with the operationswithin volumes or other data objects/structures hosted within locallyattached storage, remote storage hosted by other computing devicesaccessible over the network 626, storage provided by the distributedcomputing platform 602, etc. The storage controller 630 may replicatethe data and/or the operations to other computing devices so that one ormore replicas, such as a destination storage volume that is maintainedas a replica of a source storage volume, are maintained. Such replicascan be used for disaster recovery and failover.

The storage controller 630 may store the data or a portion thereofwithin storage hosted by the distributed computing platform 602 bytransmitting the data to the distributed computing platform 602. In oneexample, the storage controller 630 may locally store frequentlyaccessed data within locally attached storage. Less frequently accesseddata may be transmitted to the distributed computing platform 602 forstorage within a data storage tier 608. The data storage tier 608 maystore data within a service data store 620, and may store clientspecific data within client data stores assigned to such clients such asa client (1) data store 622 used to store data of a client (1) and aclient (N) data store 624 used to store data of a client (N). The datastores may be physical storage devices or may be defined as logicalstorage, such as a virtual volume, LUNs, or other logical organizationsof data that can be defined across one or more physical storage devices.In another example, the storage controller 630 transmits and stores allclient data to the distributed computing platform 602. In yet anotherexample, the client device 628 transmits and stores the data directly tothe distributed computing platform 602 without the use of the storagecontroller 630.

The management of storage and access to data can be performed by one ormore storage virtual machines (SMVs) or other storage applications thatprovide software as a service (SaaS) such as storage software services.In one example, an SVM may be hosted within the client device 628,within the storage controller 630, or within the distributed computingplatform 602 such as by the application server tier 606. In anotherexample, one or more SVMs may be hosted across one or more of the clientdevice 628, the storage controller 630, and the distributed computingplatform 602.

In one example of the distributed computing platform 602, one or moreSVMs may be hosted by the application server tier 606. For example, aserver (1) 616 is configured to host SVMs used to execute applicationssuch as storage applications that manage the storage of data of theclient (1) within the client (1) data store 622. Thus, an SVM executingon the server (1) 616 may receive data and/or operations from the clientdevice 628 and/or the storage controller 630 over the network 626. TheSVM executes a storage application to process the operations and/orstore the data within the client (1) data store 622. The SVM maytransmit a response back to the client device 628 and/or the storagecontroller 630 over the network 626, such as a success message or anerror message. In this way, the application server tier 606 may hostSVMs, services, and/or other storage applications using the server (1)616, the server (N) 618, etc.

A user interface tier 604 of the distributed computing platform 602 mayprovide the client device 628 and/or the storage controller 630 withaccess to user interfaces associated with the storage and access of dataand/or other services provided by the distributed computing platform602. In an example, a service user interface 610 may be accessible fromthe distributed computing platform 602 for accessing services subscribedto by clients and/or storage controllers, such as data replicationservices, application hosting services, data security services, humanresource services, warehouse tracking services, accounting services,etc. For example, client user interfaces may be provided tocorresponding clients, such as a client (1) user interface 612, a client(N) user interface 614, etc. The client (1) can access various servicesand resources subscribed to by the client (1) through the client (1)user interface 612, such as access to a web service, a developmentenvironment, a human resource application, a warehouse trackingapplication, and/or other services and resources provided by theapplication server tier 606, which may use data stored within the datastorage tier 608.

The client device 628 and/or the storage controller 630 may subscribe tocertain types and amounts of services and resources provided by thedistributed computing platform 602. For example, the client device 628may establish a subscription to have access to three virtual machines, acertain amount of storage, a certain type/amount of data redundancy, acertain type/amount of data security, certain service level agreements(SLAs) and service level objectives (SLOs), latency guarantees,bandwidth guarantees, access to execute or host certain applications,etc. Similarly, the storage controller 630 can establish a subscriptionto have access to certain services and resources of the distributedcomputing platform 602.

As shown, a variety of clients, such as the client device 628 and thestorage controller 630, incorporating and/or incorporated into a varietyof computing devices may communicate with the distributed computingplatform 602 through one or more networks, such as the network 626. Forexample, a client may incorporate and/or be incorporated into a clientapplication (e.g., software) implemented at least in part by one or moreof the computing devices.

Examples of suitable computing devices include personal computers,server computers, desktop computers, nodes, storage servers, storagecontrollers, laptop computers, notebook computers, tablet computers orpersonal digital assistants (PDAs), smart phones, cell phones, andconsumer electronic devices incorporating one or more computing devicecomponents, such as one or more electronic processors, microprocessors,central processing units (CPU), or controllers. Examples of suitablenetworks include networks utilizing wired and/or wireless communicationtechnologies and networks operating in accordance with any suitablenetworking and/or communication protocol (e.g., the Internet). In usecases involving the delivery of customer support services, the computingdevices noted represent the endpoint of the customer support deliveryprocess, i.e., the consumer's device.

The distributed computing platform 602, such as a multi-tenant businessdata processing platform or cloud computing environment, may includemultiple processing tiers, including the user interface tier 604, theapplication server tier 606, and a data storage tier 608. The userinterface tier 604 may maintain multiple user interfaces, includinggraphical user interfaces and/or web-based interfaces. The userinterfaces may include the service user interface 610 for a service toprovide access to applications and data for a client (e.g., a “tenant”)of the service, as well as one or more user interfaces that have beenspecialized/customized in accordance with user specific requirements,which may be accessed via one or more APIs.

The service user interface 610 may include components enabling a tenantto administer the tenant's participation in the functions andcapabilities provided by the distributed computing platform 602, such asaccessing data, causing execution of specific data processingoperations, etc. Each processing tier may be implemented with a set ofcomputers, virtualized computing environments such as a storage virtualmachine or storage virtual server, and/or computer components includingcomputer servers and processors, and may perform various functions,methods, processes, or operations as determined by the execution of asoftware application or set of instructions.

The data storage tier 608 may include one or more data stores, which mayinclude the service data store 620 and one or more client data stores.Each client data store may contain tenant-specific data that is used aspart of providing a range of tenant-specific business and storageservices or functions, including but not limited to ERP, CRM, eCommerce,Human Resources management, payroll, storage services, etc. Data storesmay be implemented with any suitable data storage technology, includingstructured query language (SQL) based relational database managementsystems (RDBMS), file systems hosted by operating systems, objectstorage, etc.

In accordance with one embodiment of the invention, the distributedcomputing platform 602 may be a multi-tenant and service platformoperated by an entity in order to provide multiple tenants with a set ofbusiness related applications, data storage, and functionality. Theseapplications and functionality may include ones that a business uses tomanage various aspects of its operations. For example, the applicationsand functionality may include providing web-based access to businessinformation systems, thereby allowing a user with a browser and anInternet or intranet connection to view, enter, process, or modifycertain types of business information or any other type of information.

In an embodiment, the described methods and/or their equivalents may beimplemented with computer executable instructions. Thus, In anembodiment, a non-transitory computer readable/storage medium isconfigured with stored computer executable instructions of analgorithm/executable application that when executed by a machine(s)cause the machine(s) (and/or associated components) to perform themethod. Example machines include but are not limited to a processor, acomputer, a server operating in a cloud computing system, a serverconfigured in a Software as a Service (SaaS) architecture, a smartphone, and so on). In an embodiment, a computing device is implementedwith one or more executable algorithms that are configured to performany of the disclosed methods.

It will be appreciated that processes, architectures and/or proceduresdescribed herein can be implemented in hardware, firmware and/orsoftware. It will also be appreciated that the provisions set forthherein may apply to any type of special-purpose computer (e.g., filehost, storage server and/or storage serving appliance) and/orgeneral-purpose computer, including a standalone computer or portionthereof, embodied as or including a storage system. Moreover, theteachings herein can be configured to a variety of storage systemarchitectures including, but not limited to, a network-attached storageenvironment and/or a storage area network and disk assembly directlyattached to a client or host computer. Storage system should thereforebe taken broadly to include such arrangements in addition to anysubsystems configured to perform a storage function and associated withother equipment or systems.

In some embodiments, methods described and/or illustrated in thisdisclosure may be realized in whole or in part on computer-readablemedia. Computer readable media can include processor-executableinstructions configured to implement one or more of the methodspresented herein, and may include any mechanism for storing this datathat can be thereafter read by a computer system. Examples of computerreadable media include (hard) drives (e.g., accessible via networkattached storage (NAS)), Storage Area Networks (SAN), volatile andnon-volatile memory, such as read-only memory (ROM), random-accessmemory (RAM), electrically erasable programmable read-only memory(EEPROM) and/or flash memory, compact disk read only memory (CD-ROM)s,CD-Rs, compact disk re-writeable (CD-RW)s, DVDs, cassettes, magnetictape, magnetic disk storage, optical or non-optical data storage devicesand/or any other medium which can be used to store data.

Although the subject matter has been described in language specific tostructural features or methodological acts, it is to be understood thatthe subject matter defined in the appended claims is not necessarilylimited to the specific features or acts described above. Rather, thespecific features and acts described above are disclosed as exampleforms of implementing at least some of the claims.

Various operations of embodiments are provided herein. The order inwhich some or all of the operations are described should not beconstrued to imply that these operations are necessarily orderdependent. Alternative ordering will be appreciated given the benefit ofthis description. Further, it will be understood that not all operationsare necessarily present in each embodiment provided herein. Also, itwill be understood that not all operations are necessary in someembodiments.

Furthermore, the claimed subject matter is implemented as a method,apparatus, or article of manufacture using standard application orengineering techniques to produce software, firmware, hardware, or anycombination thereof to control a computer to implement the disclosedsubject matter. The term “article of manufacture” as used herein isintended to encompass a computer application accessible from anycomputer-readable device, carrier, or media. Of course, manymodifications may be made to this configuration without departing fromthe scope or spirit of the claimed subject matter.

As used in this application, the terms “component”, “module,” “system”,“interface”, and the like are generally intended to refer to acomputer-related entity, either hardware, a combination of hardware andsoftware, software, or software in execution. For example, a componentincludes a process running on a processor, a processor, an object, anexecutable, a thread of execution, an application, or a computer. By wayof illustration, both an application running on a controller and thecontroller can be a component. One or more components residing within aprocess or thread of execution and a component may be localized on onecomputer or distributed between two or more computers.

Moreover, “exemplary” is used herein to mean serving as an example,instance, illustration, etc., and not necessarily as advantageous. Asused in this application, “or” is intended to mean an inclusive “or”rather than an exclusive “or”. In addition, “a” and “an” as used in thisapplication are generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Also, at least one of A and B and/or the like generally means A orB and/or both A and B. Furthermore, to the extent that “includes”,“having”, “has”, “with”, or variants thereof are used, such terms areintended to be inclusive in a manner similar to the term “comprising”.

Many modifications may be made to the instant disclosure withoutdeparting from the scope or spirit of the claimed subject matter. Unlessspecified otherwise, “first,” “second,” or the like are not intended toimply a temporal aspect, a spatial aspect, an ordering, etc. Rather,such terms are merely used as identifiers, names, etc. for features,elements, items, etc. For example, a first set of information and asecond set of information generally correspond to set of information Aand set of information B or two different or two identical sets ofinformation or the same set of information.

Also, although the disclosure has been shown and described with respectto one or more implementations, equivalent alterations and modificationswill occur to others skilled in the art based upon a reading andunderstanding of this specification and the annexed drawings. Thedisclosure includes all such modifications and alterations and islimited only by the scope of the following claims. In particular regardto the various functions performed by the above described components(e.g., elements, resources, etc.), the terms used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure. In addition, while aparticular feature of the disclosure may have been disclosed withrespect to only one of several implementations, such feature may becombined with one or more other features of the other implementations asmay be desired and advantageous for any given or particular application.

What is claimed is:
 1. A method comprising: generating an objectcomprising data of compressed block numbers; generating an indicator toindicate that the object comprises the data of the compressed blocknumbers; and storing the object within an object store.
 2. The method ofclaim 1, comprising: populating a mapping metafile with an entry for ablock number of data stored within the object, wherein the entry mapsthe block number to a cloud block number associated with the objectstore.
 3. The method of claim 2, comprising: populating the entry with acompression indicator to indicate whether data of the block number iscompressed.
 4. The method of claim 2, comprising: populating the entrywith a compression group start indicator to indicate whether the blocknumber is a starting block number for a compression group of a pluralityof block numbers of the compressed data blocks.
 5. The method of claim2, comprising: populating the entry with an overflow indicator toindicate whether the data block has an overflow entry within an overflowmapping metafile.
 6. The method of claim 2, comprising: populating theentry with a logical length of an extent associated with the blocknumber.
 7. The method of claim 2, comprising: populating the entry witha physical length of an extent associated with the block number.
 8. Themethod of claim 1, wherein the compressed block numbers corresponding toprimary storage remote from the object store.
 9. The method of claim 8,comprising: indexing a mapping metafile by the compressed block numbersof the primary storage, wherein a compressed block number corresponds toa virtual volume block number.
 10. A non-transitory machine readablemedium comprising instructions for performing a method, which whenexecuted by a machine, causes the machine to: generate an objectcomprising data of compressed block numbers of data stored within theobject; generate an indicator to indicate that the object comprises thedata of the compressed block numbers; and store the object within anobject store.
 11. The non-transitory machine readable medium of claim10, wherein the instructions cause the machine to: populate a mappingmetafile with an entry for a block number, wherein the entry maps theblock number to a cloud block number associated with the object store.12. The non-transitory machine readable medium of claim 11, wherein theinstructions cause the machine to: populate the entry with a compressionindicator to indicate whether data of the block number is compressed.13. The non-transitory machine readable medium of claim 11, wherein theinstructions cause the machine to: populate the entry with a compressiongroup start indicator to indicate whether the block number is a startingblock number for a compression group of a plurality of block numbers ofthe compressed data blocks.
 14. The non-transitory machine readablemedium of claim 11, wherein the instructions cause the machine to:populate the entry with an overflow indicator to indicate whether thedata block has an overflow entry within an overflow mapping metafile.15. The non-transitory machine readable medium of claim 11, wherein theinstructions cause the machine to: populate the entry with a logicallength of an extent associated with the block number.
 16. Thenon-transitory machine readable medium of claim 11, wherein theinstructions cause the machine to: populate the entry with a physicallength of an extent associated with the block number.
 17. Thenon-transitory machine readable medium of claim 10, wherein thecompressed block numbers corresponding to primary storage remote fromthe object store.
 18. The non-transitory machine readable medium ofclaim 17, wherein the instructions cause the machine to: index a mappingmetafile by the compressed block numbers of the primary storage, whereina compressed block number corresponds to a virtual volume block number.19. A computing device, comprising: a memory comprising machineexecutable code; and a processor coupled to the memory, the processorconfigured to execute the machine executable code to cause the processorto: generate an object comprising data of compressed block numbers ofdata stored within the object; generate an indicator to indicate thatthe object comprises the data of the compressed block numbers; and storethe object within an object store.
 20. The computing device of claim 19,wherein the machine executable code causes the processor to: populate amapping metafile with an entry for a block number, wherein the entrymaps the block number to a cloud block number associated with the objectstore.